Tonometer



. Jan. 14 1930. LA FORCE 1,743,461

TONOMETER Fil'ed May 4, 1927 J lfin ior 12.15 r'ce 43 14w:

Patented Jan. 14, 1930 BURDETTE D. LA FORGE, OF OT'IUM'WA, IOVJA TONOMETER Application filed May 4,

My invention is a tonometer to be used in determining the intraocular pressure.

An object of my invention is the construc tion of a tonometer which may be placed on the eyelid to obtain the intraocular pressure and hence overcome the necessity of applying a local anaesthetic or the like to the eye when the intraocular pressure has to be obtained with the open eye.

Another object of my invention is the construction of a tonometer having a plurality of movable parts so that these parts engage the eye concentrically and by their relative position, as read on the scale, give a reading from which may be interpreted the intraocular pressure.

In constructing my device I utilize an outside tube or cylinder and in this mount another sliding cylinder, this sliding cylinder having a centrally positioned slidable rod.

The slidable rod is weighted to a greater extent than the slidable cylinder and when the device is rested on the closed eyelid a reading may be obtained of the intraocular pressure.

This is due to the weighted rod pressing the eyeball inwardly to a greater or lesser extent than the sliding cylinder, in accordance with the internal pressure of the eye.

My invention is more fully illustrated in the accompanying drawings, in which:

Figure 1 is a perspective view of my invention showing the manner of applying it to the closed eyelid over the eyeball.

Figure 2 is a side elevation of my tonometer partly broken away.

Figure 3 is a longitudinal section on the line 33 of Fig. 2 in the direction of the arrows.

Figure 4: is a perspective view of the tube 1927. Serial No. 188,711.

able plug 15 at the other end. The tube has a narrow longitudinal slot 16 on one side and a relatively large opening 17 on the other side. tion 18 to or casing.

The weighted cylinder 19 has a weight 20 There is also preferably a knurled secallow facility in gripping the tube at the upper portion which may be formed by thickening the wall of this cylinder or by slipping a tight fitting cylinder over the cylinder part 19 and fastening it thereto in any suitable manner.

This cylinder has an elongate-d slot 21 on one side and a slot 22 on the opposite side walls, and through this latter slot is fitted a pin 23 having a finger engaging end or button 24 There are a series of graduations 25 on the cylinder adjacent the slot 21. The cylinder 19 has an inwardly beveled end 26 forming its lower edge.

The welghted rod 27 has a weight 28 secured to its upper end, this preferably being by having a screw threaded stem29 on the upper end of the main portion of the rod and this fitting into a socket 3,0 in the weight.

order to obtain accurate adjustments of the weight, this may have a hollowed out section 31 at the poured or a lead filling scraped out.

rod has a top in which molten lead may be The stud 32 secured thereto in the side,

cylinder 19 to limit the relative movement of the weighted rod and the cylinder. 'A graduation mark 33 is provided on the rodto register with the indicating markings 25 on the cylinder.

The lower end of the rod is preferably tapered as indicated at-34 and has a squared end 35.

In order to hold the weighted cylinder and weighted rod in adjusted position independently of the button 24, I provide a clamp screw 36.

This clamp screw is secured in the weighted rod and passes through a slot- 37 in the weighted cylinder and through a slot 38 in the thereto.

casing 11 and hasa nut 39 secured After the adjustment on the eye has been obtained, the operator may take a reading by looking through the large opening 17 which is in a position for ready mspection, as shown in Fig. 1, and if he desires to maintain the parts with this reading he may screw down the clamp nut 39 thereby securing the weighted rod and the weighted cylinder in the relative position of the reading. An alternative procedure is by utilizing the button- 24- as hereunder explained,

The manner of using and functioning of my tonometer is substantially as follows:

The patient will be placed with the head in a reclining position, as shown in Fig. 1, and closes the eyelid, thus protecting the eyeball from injury and allowing use of the instrument directly on the eyelid instead of on the open eye. It is .well known that instruments used on the open eyerequire an anaesthetic or the like to be applied to the eyeball. The weighted cylinder and the weighted rod are slid inwardly in the tubular casing 11 until they are insidethe lower open end 12 and the device is placed over the eye. The control of the weighted cylinder and the rod is by means of the button 24. It will be seen that when thebutton is pressed inwardly it presses the side of the rod against the inside of the cylinder and displaces this 7 33 in relation to the graduations 25, as shown in Fig. 6,, this being visible throughthe cut out section or opening 17 in the tubular casa It will be seen by the illustration of 6 that as the cylinder 19 is of lighter weight than the weighted rod and has a greater bearing area on the eyelid it thus reent from the normal in that the eyeball may ceives a greater support from the eyeball than does the narrow end 35 of the weighted rod. Therefore this rod gives a concentrated weight in the center ofthe circle formed by the end 26 of thecylinder- 19 and as the eyeball is more or less soft it becomes depressed, hence givinga reading showing a normal condition of the eyeball, or one which is difi'erbe too soft or too hard; i

As the eyeball is spherical, ,and'if the device were placed on a hard sphere, the end of the rod would be thrust slightly inwardly of the end26 of the cylinder 19 and,

if the eyeball is very hard,'indicating an:

other abnormal condition, the weighted r'od would give a reading indicating this condider 19 and the rod 27 together, and holding them in this position remove them until it is convenient to obtain the reading.

I have not designated in the above description the particular calibrations of the readings but the device will be calibrated to read in the ordinary manner of tonometers for testing the internal pressure of the eyeball. Q

It is apparent that my device may be changed and modified insize, etc.,' so as to obtain abdominal pressures and those of other parts of the body for which a device of a tonometer character may be utilized. s

A characteristic feature of my invention is the simplicity of the device in that onl three relatively moving parts are employe these being the outer tubular casing which may be regarded as a stationary element, the so cylinder therein and the weighted rod slidable inside of the cylinder.

Another characteristic feature of my invention is-that the cylinder and the weighted rod may be adjusted by pressing on the button 24 before the device is adjusted to a persons eye; and, when the end of the cylinder is adjusted over the eyelid, the weighted rod may be gently lowered. In addition to being able to obtain a reading due to the gradua- 1 tions on the cylinder and on the rod, the operator may hold these two relatively movable elements in the position of the indicator and remove the device from'the eye, holding the button 24 until he may obtain a reading. ins

This is a feature which is of manifest advantage, as in some ailments of the eye it is necessary for the patient to be in a very dark room, where it is diificult for the operator to obtain,

a readin In such case the operator may, after ad usting the tonometer, remove the instrumentto a suitable place for obtaining the readings.

In addition to this feature, the rod, the. 7 cylinder and the outer tubular casing may be clamped together by means of the ,clamp nut 39 operating on the clamp screw 36, this securing these parts together so that after adjustment, the reading may be obtained in a} better light or at a more convenient time than when making the testof a patients eye.

Various changes may be madein the principles of my invention without departing from the spirit thereof, as set forth in the. description, drawings andclaims. y

1. A surgical instrument; having a cylindrica-l structure, a rod slidably mounted therein, the rod being of greater weight'than,

the cylinder, means to register the relative position of the rod and cylinder when at rest on the part or" the body being tested, and means to retain the rod and the cylinder in such registering position after removal from the body.

2. A surgical instrument having a relatively slidable cylinder and a Weighted rod concentric therein, graduations on the cylinder, said cylinder having a slot and the rod having a graduation visible therethrough adjacent the graduations on the cylinder, and a manually operated device to retain and hold the rod in adjusted relation to the cylinder.

3. A surgical instrument having outer tubular casing with a large opening in one side and a slot in the other side, a slidable cylinder therein having a series of graduations visible through the opening, the cylinder having a slot adjacent the graduations, a weighted rod slidable in the cylinder having a graduation visible through the slot in the cylinder and readable with the gradua tions on the cylinder, a pin secured to the weighted rod and slidable through a second slot in the cylinder and through the slot in the casing, and means to manipulate the pin to retain the rod and the cylinder in relative position when used to test part of the body.

i. A surgical instrument, as claimed in claim 3, a clamping device interconnecting the rod, the cylinder and the casing, to positively secure said parts in their relatively adjusted position.

5. A surgical instrument, as claimed in claim 3, a clamp screw secured to the rod slidable through slots in the cylinder and casing, and a nut on the outside of the casing to clamp said screw and thereby hold the rod, the cylinder and the casing, in adjusted position.

6. A surgical instrument having a tubular casing with an internal bead at the lower end, a large opening at one side, a slot on another side, a slidable cylinder having a bearing on said bead, said cylinder having graduations visible through the opening, and having a slot adjacent said graduations and another slot to register with the slot of the casing, a rod slidable in the cylinder and having a weight on its inner end, the weight sliding against the casing, said rod having a graduation visible through one of the slots in the cylinder and the opening in the casing, a pin secured to the rod extending through one of the slots in the cylinder and the slot in the casing, a button on the end of the pin to allow pressing the rod and the cylinder sidewise to retain said rod and cylinder in relative adjusted position when testing part of the body.

7 A surgical instrument, as claimed in claim 6, and a positive clamping device inposition independent of an actuation by the pin. 7

8. A surgical instrument having a tubular structure and a rod slidable concentric therewith, means to obtain a reading of the relative position of the tubular structure and the rod when at rest on the part of the body being tested, guide means for the tubular structure and the rod, adapted to be supported on the body spaced from the part being tested and thereby cause no weight on such part, whereby the adjusting of the tubular structure and the slidable rod on the part of the body being tested as to its compressibility may be effected without the guiding means eflecting such compressibility.

9. A surgical instrument having an outer tubular casing, a cylinder slidable therein, a

weighted rod slidable in the cylinder, said outer casing being adapted for support on a body at a distance from the particular part to be tested as to its compressibility, means to manipulate the cylinder and rod on the part of the body to be tested as to its compressibility, and means to obtain a reading of the relative position of the cylinder and the rod When at rest on the part of the body being tested.

10. A surgical instrument as claimed in claim 9 and a manually operated device to hold and retain the cylinder and the rod in their relative position after removal from the body.

In testimony whereof I have signed my name to this specification,

B. D. LA FORCE.

terconnecting the rod, the cylinder and the 

